The present invention pertains primarily to mechanical lifting devices, and more particularly to jacking devices for use with trailers or the like.
Generally, lifting jacks are made in many different types and sizes, ranging from small jacking devices used for leveling and supporting work on wood planers to powerful hydraulic jacks capable of lifting a locomotive or even greater weights. The mechanisms used in the different types of jacks also vary greatly, with one of the more popular types consisting of a lifting screw which is inserted in a suitable base. Other types include the gear-and-rack and the lever-and-rack types, in addition to the many different designs that are hydraulically operated. While the lifting capacity varies greatly, in general, screw-type jacks and those belonging to the reduction gear-and-rack class are capable of lifting loads of several tons, whereas those operated by hydraulic power ordinarily are capable of lifting much more than that. The present invention relates primarily to screw, lever, or gear-type jacks, although it is contemplated that the basic idea of the invention might also be applied to other types of jacking devices.
Except for scissors or tripod-type jacks, most conventional jacking devices for use with trailers, automobiles, trucks, campers, and the like comprise a vertical member having a base for supporting the jack and an engaging member somehow mounted on the vertical member which may be either attached to, or positioned under the object to be lifted. The engaging member is moved upwardly along the vertical member by way of whatever jacking mechanism is selected, thereby lifting the object. For example, in order to lift an automobile to remove a wheel, the engaging member might be positioned under the car's bumper, and then moved up the vertical member by means of a lever-and-rack mechanism. In order to level a small trailer, the engaging member might be either positioned under the trailer frame or under the front tow bar or tongue, and then moved up the vertical member by means of a continuous screw mechanism.
Typical of one of the jacking devices currently used with many travel-type trailers is a jack having a generally square bottom and an upper pyramid-like structure. The upper "pointed" portion of the pyramid frame is threaded so as to accept a threaded support pipe which is then rotated via a rod handle passing through it. In this way the support pipe is slowly moved upwardly into engagement with a trailer frame in order to level or stabilize it by raising it to an appropriate height. In addition to being clumsy and difficult to use, this type of device is not self-storing and must be physically removed from the underside of the trailer and somehow stored every time the trailer is moved. Of course, the trailer owner would have to repeatedly crawl under the trailer to position this type of jack and likewise have to repeatedly crawl in and out to check on his leveling efforts. Although two such leveling jacks are normally supplied with most travel trailers, usually four are necessary to adequately level and support a parked trailer. Storing such jacks in trailer storage compartments takes up valuable space which might better be used to store other necessities.
An additional feature present on some jacking devices is both a rough and fine adjustment of the engaging member. The use of both a rough and fine adjustment does away with the need for having to raise the jack by way of a single, slow operating, and continuous jacking mechanism. The rough adjustment allows selection of intermediate levels closer to the final desired height. Normally, such a feature is somehow built into the vertical member or engaging member so that a rough height adjustment may first be made to align the engaging member with the object to be lifted. The regular jacking mechanism which provides a finer, continuous height adjustment is then used to actually lift the object. Most such devices, however, require that the rough adjustment be an integral part of the vertical member and thus the cost and clumsiness of the device is substantially increased. Also, most such devices do not allow attachment to the object being lifted prior to making the rough adjustment, which often significantly hampers operation of the jacking device and also complicates storage.
Accordingly, it is a principle object of the present invention to provide an improved jacking device for use with trailers or the like which allows both rough and fine adjustments, integral storage capability, and easy adaptability to various mounting configurations.
In general, the jacking device of the present invention comprises an upright vertical housing and includes means for moving a support base and inner telescoping member in said vertical housing from a retracted position to an extended position, so that the overall length of the jacking device is increased. A rough adjusting column is provided which is spaced apart from and secured to the exterior of the upright vertical housing. This rough adjusting column includes an engaging member movably mounted thereon for contacting the object to be lifted and also includes means for locating and securing the engaging member at various positions along the column so that a rough height adjustment may be made prior to using the regular jacking mechanism to make the final height adjustments. A plurality of longitudinally spaced holes extending transversely through the rough adjusting column may be provided and a complimentary pair of holes extending transversely through the portion of the engaging member which is slidably mounted on the column may also be provided, with all the holes being transversely aligned so that a locating pin may be inserted through the holes to secure the engaging member at a desired height. This would set the rough adjusting feature of the present invention with the fine adjustment being carried out by the use of a conventional jacking mechanism contained in the upright vertical housing of the jacking device. The present invention is especially suitable for use with travel-type trailers and such use will be described herein. However, it is to be understood that the present invention is equally applicable to other jacking arrangements.
Additional advantages and features of the present invention will become apparent from a reading of the detailed description of the preferred embodiment which makes reference to the following set of drawings in which :